Electroplating processor with vacuum rotor

ABSTRACT

A substrate processor uses pressurized gas to create a vortex for lifting and holding a wafer, and to create a vacuum to prevent the wafer from adhering to a contact ring seal after electroplating the wafer. A processor head has a rotor movable into and out of an electrolyte vessel. A backing plate on the rotor includes vortex outlets which create the vortex in the rotor. A vacuum channel adjacent to the perimeter of the rotor applies vacuum to the wafer edges to hold the wafer onto the backing plate. A solenoid or switch in the head has a first position to supply gas flow to the vortex outlets, and a second position to supply gas flow to an aspirator which creates the vacuum in the vacuum channel.

TECHNICAL FIELD

This application relates to chambers, systems, and methods for electroplating substrates.

BACKGROUND OF THE INVENTION

Microelectronic devices such as semiconductor devices are generally fabricated on and/or in substrates or wafers. In a typical fabrication process, one or more layers of metal or other conductive materials are formed on a wafer in an electroplating processor. The processor may have a bath of electrolyte held in vessel or bowl, with one or more anodes in the bowl. The wafer itself may be held in a rotor in a head movable into the bowl for processing and away from the bowl for loading and unloading. A contact ring on the rotor generally has a large number of contact fingers that make electrical contact with the wafer. A seal may be used to seal the fingers from contact with the electrolyte, to avoid plating metal onto the fingers. After the electroplating step, the wafer must be removed from the rotor. Under certain conditions, the wafer may adhere to the seal, making removal of the wafer more time consuming and complicated, as well as risking damage to the wafer. Accordingly, improved processors and methods are needed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, the same element number indicates the same element in each of the views.

FIG. 1 is a perspective view of an electroplating processor.

FIG. 2 is an exploded perspective view of the head of the processor shown in FIG. 1.

FIG. 3 is a top view of the head shown in FIG. 2, with the head cover removed for purpose of illustration.

FIG. 4 is a top perspective view of the rotor of the head shown in FIGS. 2 and 3.

FIG. 5 is a bottom perspective view of the rotor of the head shown in FIG. 4.

FIG. 6 is a section view of the head shown in FIGS. 1-5 in a vortex operation position.

FIG. 7 is a rotated view of the section shown in FIG. 6.

FIG. 8 is a section view of the head shown in FIGS. 1-5 in a vacuum operation position.

FIG. 9 is a rotated view of the section shown in FIG. 8.

FIG. 10 is an enlarged detail view of the rotor shown in FIGS. 1-5 with the ring contact in the closed or up position as used in processing.

FIG. 11 is an enlarged detail view of the rotor shown in FIGS. 1-5 with the ring contact in the open or down position as used for loading and unloading.

FIG. 12 is a schematic diagram of the head shown in FIGS. 1-5.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an electroplating processor 40 supported on a deck 38 of a processing system, which may have arrays of processors 40. One or more robots may load and unload wafers into and out of the processors 40, as described for example in U.S. Pat. No. 7,371,306. In the example shown the processor 40 has a head 50 which may be raised and lowered to move a wafer held in a rotor 64 into and out of a bowl or vessel 60 containing an electrolyte. An agitator 62 may optionally be provided in the bowl in some applications. A contact ring 65 on the rotor 64 may be movable between an open or down position for loading and unloading, schematically shown in FIGS. 1 and 11, and an up or closed position for processing, as shown in FIGS. 6-10.

Referring to FIGS. 1 and 2, the head 50 may have a lift arm 56 and a cover 54 attached to a head housing 52. A flex line 58 provides electrical power and pressurized gas, such as air, to the head 50. Turning to FIGS. 3-6, the head may include a motor 68 for rotating the rotor 64 having a rotor plate 74 on a backing plate 72, with a rotor shaft 70 connecting the rotor plate 74 to the motor 68.

A gas operated wafer handling system 80 may be provided in the rotor 64. In general terms, the system 80 uses a flow of compressed gas to provide a vortex effect to lift a wafer 100 up off of a robot end effector and into the rotor, and a vacuum effect to pull the wafer up off of the contact ring 65, and specifically a contact ring seal, after a plating process. The vortex and the vacuum may both be generated within the head using a single common supply of compressed gas or air supplied to the head 50.

As shown in FIG. 12, the gas operated wafer handling system 80 may include a solenoid or similar switch 82 for switching an incoming supply of gas between a vortex line 120 and an aspirator 84. The vortex line 84 is connected to vortex/purge ports 122 in the backing plate 72, as best shown in FIG. 5. The aspirator 84 may be connected to a vacuum switch 86 and a vacuum pad 104 movable to connect with and separate from a vacuum pad landing 106 shown in FIGS. 6 and 7. When the vacuum pad 104 is moved into contact with the vacuum pad landing 106, vacuum is applied to a vacuum channel 96 around the perimeter of the backing plate 72 via a vacuum port 108, as shown in FIGS. 5 and 6. Referring to FIG. 3, the solenoid 82 toggles between a vortex/purge supply line 124 that connects to the vortex purge ports 122 and a vacuum supply line 110 that connects to the aspirator 84 for generating vacuum. The vacuum channel 96 may have multiple discrete wafer supports 94 shown in FIG. 6, or a support ring or segment, to limit bending forces applied to the edges of the wafer 100.

FIGS. 6 and 7 show the vacuum pad 104 in the up or disconnected position. FIGS. 8 and 9 show the vacuum pad 104 in the down or connected position. As shown in FIGS. 3, 7 and 12, an air cylinder 90 may be spring extended to push on a linkage arm 102 which pivots and holds the vacuum pad 104 away from the vacuum landing pad 106. When the air cylinder 90 is actuated via a supply of gas or air, the air cylinder pulls on the linkage moving the vacuum pad 104 into contact with the vacuum landing pad 106, as shown in FIGS. 8 and 9.

In use, the head 50 is lifted up off of the bowl 60 via an actuator lifting the lift arm 56. The contact ring 65 is in the open position shown in FIG. 11. A robot loads a wafer 100 into the head 50. The solenoid 82 is switched into the vortex position and the vacuum pad 104 is up. Pressurized gas flows through the solenoid 82 (or a valve controlled by the solenoid) and to the vortex/purge ports 122. This creates a low pressure zone in the rotor 50 with the gas moving in a vortex. The vortex causes the wafer 100 to be lifted up into or onto the backing plate 72. The vortex gas flows out of the rotor via vortex outlets 120, and out of the rotor via exhaust outlets 128 shown in FIG. 10. The robot then withdraws.

A check step may then optionally be performed to confirm the presence of a wafer in the head, by switching the solenoid 82 momentarily into the vacuum position. In this position, a main flow of gas or air is provided to the aspirator 84, with a secondary flow via a T-connection going to the air cylinder 90. This causes a flow of gas to actuate the air cylinder 90 moving the vacuum pad 104 down into contact with the vacuum pad landing 106, with the aspirator 84 providing vacuum to the vacuum pad 104. With the vacuum pad 104 connected to the vacuum pad landing 106, vacuum is applied to the vacuum channel 96.

Since the vacuum pad landing 106 rotates with the backing plate 72 on the rotor 50, and the vacuum pad 104 does not, the rotor is indexed via control of the motor 68 to bring them into alignment, before actuating the air cylinder 90. A hole in the rotor connects to the vacuum channel 96 which is aligned with the vacuum pad 104. If liquid is drawn into the vacuum system, it is routed to the exhaust for removal or return to the bowl.

A vacuum is established if a wafer is present. The vacuum switch 86 detects the presence of vacuum indicating the presence of a wafer. If no wafer is present, or if the wafer is broken or out of position, air leaks into the vacuum channel to cause the vacuum switch to detect reduced or no vacuum, indicating an error condition. If the check step is performed, the ring, wafer and rotor may close before switching from vortex to vacuum to run the check step. This avoids potential for the wafer to drop due to a time lag between vortex shutoff and establishing the vacuum. \

After the check step, if any, the contact ring 65 is pulled up towards the backing plate 72. This movement brings the wafer 100 into contact with contact fingers 66 and a seal 76 on the contact ring 65 shown in FIGS. 10 and 11. The head 50 is then lowered to move the wafer 100 into electrolyte contained in the bowl 60. Electrical current flows from one or more anodes in the bowl 60 through the electrolyte and through the wafer 100, as the contact ring 65 is connected to a cathode. Metal ions in the electrolyte deposit out onto the wafer forming a metal layer on the front (down facing) side of the wafer. During this electroplating processing step, the solenoid 82 may be switched to the vortex position, to provide a flow of purge gas out from the vortex/purge ports 122. If used, this flow of purge gas may help to keep the back side of the wafer clean and dry, by blocking egress of processing liquid or vapors.

After processing the head 50 is lifted away from the bowl 60 the contact ring 65 is moved back down. If the wafer adheres to the seal 76, the wafer will then not be in position to be removed from the rotor by the robot. Rather, the wafer 100 must remain with the backing plate as the contact ring seal moves down. Since the vortex effect applies force more towards the center of the wafer, as opposed to the edges, it is not well adapted for holding the wafer onto the backing plate against the pulling force of the seal 76.

To more effectively hold an adhering wafer onto the backing plate, the solenoid 82 is switched into the vacuum position. This causes the air cylinder 90 to actuate, which moves the vacuum pad 104 down onto the vacuum pad landing. 106. As a result, the vacuum channel 96 is connected to vacuum generated by the aspirator 84. The vacuum force may be larger than the vortex force. In addition, the vacuum force acts at or very close to the seal, at the edges of the wafer. Accordingly the vacuum channel may securely hold the wafer 100 onto the backing plate, without undue bending and stressing of the wafer as an adhering seal moves away.

The vacuum switch 86 senses whether the wafer has been successfully held onto the backing plate 72. The robot may then move back into the rotor, with the solenoid switched back to the vortex position, and with no gas flow provided, to allow the wafer to drop onto the robot.

As described here, the term vacuum means a partial vacuum suitable for lifting and holding a wafer. The term wafer here means any substrate or work piece on or in which microelectronic, micro-mechanical or micro-optical devices are formed.

If the backing plate 72 or the back side of the wafer is wet, the wafer may tend to stick to the backing plate via liquid surface tension. To prevent this sticking, a plastic Bellville washer or other spring element ejector 98 shown in FIGS. 6 and 7 may be provided in the vacuum channel 96 to automatically eject the wafer in the absence of vacuum or vortex holding forces. If used, the ejector element 98 may also cushion the wafer during wafer hand-off.

Table I below shows parameters as in the method described above. A mass flow controller (MFC) connected to the head via the flex line 58 supplies gas or air under pressure to the head 50 at the relative flow rates described.

MFC Vortex/Vacuum Vacuum Vacuum Flow Solenoid 82 Pad 104 Sensor 86 Wafer Hand-off Low Vortex Up off to Rotor Rotor/Ring Close low Vortex Up off Check for Wafer High Vacuum down on Process Purge Vortex Up off Sling-off Purge Vortex Up off Rotor/Ring open High Vacuum down on Wafer hand-off Off Vortex Up off to Robot

The head 50 provides for extraction of the wafer 100 regardless of any tendency of the wafer to adhere to the seal. In addition, the extraction is achieved without contacting and pulling or holding on the front side of the wafer, a technique generally not desirable or permissible in many processes.

Thus, novel apparatus and methods have been shown and described. Various changes and substitutions may of course be made without departing from the spirit and scope of the invention. The invention, therefore, should not be limited except by the following claims and their equivalents. 

1. A substrate processor, comprising: a bowl for containing an electrolyte; a head having a rotor movable into and out of the bowl; a plurality of vortex outlets in the rotor between a center of the rotor and a perimeter of the rotor; a vacuum channel adjacent to the perimeter of the rotor; a switch in the head having a first position wherein a flow of pressurized gas is supplied to the vortex outlets, and a second position wherein a flow of pressurized gas is supplied to an aspirator creating a vacuum in the vacuum channel.
 2. The substrate processor of claim 1 with the switch comprising a solenoid.
 3. The substrate processor of claim 1 further comprising an actuator in the head operable via gas flow when the switch is in the second position.
 4. The substrate processor of claim 3 with the rotor including a backing plate and with the plurality of vortex outlets and the vacuum channel in the backing plate.
 5. The substrate processor of claim 4 with the rotor further including a contact ring movable towards and away from the backing plate.
 6. The substrate processor of claim 5 with the actuator linked to a vacuum pad connected to the aspirator, and with the vacuum pad spaced apart from the backing plate when the switch is in the first position, and with the vacuum pad moved into contact with a vacuum pad landing on the backing plate when the switch is in the second position.
 7. The substrate processor of claim 6 with actuator spring biased to hold the vacuum pad spaced apart from the backing plate.
 8. The substrate processor of claim 1 further comprising a wafer ejector in the vacuum channel.
 9. The substrate processor of claim 8 with the wafer ejector comprising a spring.
 10. The substrate processor of claim 9 with the spring comprising a non-metallic Bellville washer.
 11. The substrate processor of claim 1 further comprising a vacuum sensor in the head for sensing a vacuum in the vacuum channel.
 12. A substrate processor, comprising: a vessel; one or more electrodes in the vessel; a head having a rotor including a backing plate having a plurality of vortex outlets, and a vacuum channel adjacent to the perimeter of the backing plate; a contact ring on the head movable axially from a load/unload position spaced apart from the backing plate, to a process position adjacent to the backing plate, with the contact ring having a plurality of contact fingers and a seal for sealing the contact fingers from electrolyte in the vessel; a head lifter for moving the head towards and away from the vessel; a pressurized gas line leading into the head; and a solenoid in the head switchable between a first position wherein a flow of pressurized gas is supplied from the pressurized gas line to the vortex outlets, and a second position wherein a flow of pressurized gas is supplied to an aspirator and an actuator to create a vacuum in the vacuum channel.
 13. The processor of claim 12 with the actuator moving a vacuum pad to connect to, and separate from, a vacuum port in the backing plate connected to the vacuum channel.
 14. A method for processing a wafer, comprising moving the wafer into a head of a processor; lifting the wafer into contact with the head using a gas vortex; moving a contact ring on the head into contact with the wafer; placing the wafer in an electrolyte and sealing the electrolyte from the contact ring via a seal; passing electrical current through the electrolyte to form a layer of conductive material on the wafer; applying vacuum to the perimeter of the wafer to hold the wafer onto the backing plate; moving the contact ring away from the backing plate, with the wafer remaining on the backing plate; and removing the wafer from the processor.
 15. The method of claim 14 further including indexing the rotor to align a vacuum pad in the head with a vacuum pad landing on the backing plate. 